The storage vendor, HP, had suggested making a software raid using the multipath option to achieve the desired functionality and we followed it. There seemed to be some conflict with the device-mapper tools and the md raid devices were being stopped after initialisation but making a new initrd image helped and solved the problem. Thanks for the link the the presentation but I could not find the English translation.
Also you should always use a odd number of member (like
3,5,7,...), because the fencing is then better. But when you have a real HA
Solution, in the most of the Time you have also Two Datacenters. And then the
Cluster should also work when one Datacenter is not available. Then you need
either a new Datacenter ;-), for the third member or you fail back to the
Problem with the fencing! And then maybe the quorum disk is the best
I am forced to go ahead with two nodes only. Will update the forum once everything is in place and working.Thank you very much for your suggestions.